mash: Migrate ScopedTargetRootWindow to //ash/common

ash/common/wm_shell.cc

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ash/common/wm_shell.h"
 
 #include <utility>
 
 #include "ash/common/accelerators/accelerator_controller.h"
 #include "ash/common/accelerators/ash_focus_manager_factory.h"
@@ skipping 149 matching lines @@
         return true;
       }
     }
   }
   return false;
 }
 
 void WmShell::ShowAppList() {
   // Show the app list on the default display for new windows.
   int64_t display_id =
-      GetRootWindowForNewWindows()->GetDisplayNearestWindow().id();
+      root_window_for_new_windows_->GetDisplayNearestWindow().id();
   delegate_->GetAppListPresenter()->Show(display_id);
 }
 
 void WmShell::DismissAppList() {
   delegate_->GetAppListPresenter()->Dismiss();
 }
 
 void WmShell::ToggleAppList() {
   // Show the app list on the default display for new windows.
   int64_t display_id =
-      GetRootWindowForNewWindows()->GetDisplayNearestWindow().id();
+      root_window_for_new_windows_->GetDisplayNearestWindow().id();
   delegate_->GetAppListPresenter()->ToggleAppList(display_id);
 }
 
 bool WmShell::IsApplistVisible() const {
   return delegate_->GetAppListPresenter()->IsVisible();
 }
 
 bool WmShell::GetAppListTargetVisibility() const {
   return delegate_->GetAppListPresenter()->GetTargetVisibility();
 }
@@ skipping 63 matching lines @@
 void WmShell::DeleteToastManager() {
   toast_manager_.reset();
 }
 
 void WmShell::SetAcceleratorController(
     std::unique_ptr<AcceleratorController> accelerator_controller) {
   accelerator_controller_ = std::move(accelerator_controller);
 }
 
 }  // namespace ash